Permanent magnetism of intermetallic compounds between light and heavy transition-metal elements

Abstract

First principle calculations are used to investigate the intrinsic magnetic properties of intermetallic alloys of the type XMn, where X is a 4d or 5d element and M is Fe or Co. Emphasis is on the hexagonal C14 Laves-phase 1:2 and 1:5 alloys, the latter crystallizing in the CaCu5 structure. These series are of interest in permanent magnetism from fundamental and practical viewpoints, respectively. In the former, the unit cells form a prototypical motif where a heavy atom with high spin-orbit coupling and magnetocrystalline anisotropy is surrounded by many somewhat smaller M atoms with high magnetization, and the latter are Laves-phase derivatives of renewed interest in permanent magnetism. Our DFT calculations predict magnetic moments, magnetizations and anisotropies, as well as formation energies. The results are analyzed across the 4d and 5d series, especially with respect to hybridization effects between 3d and 4d/5d bands.

Magnetic anisotropy — How much is enough for a permanent magnet?

“…New materials are being considered, and old ones reconsidered for their permanent magnet potential [15][16][17][18][19][20]. Since a reasonably large magnetization coupled with uniaxial anisotropy seems to be indispensable, it is appropriate to raise the question of just how much anisotropy is enough?…”

Hard Magnetic Off-Stoichiometric (Fe,Sb)2+xHf1−xIntermetallic Phase

“…There are several examples that illustrate the special role of RM for hard magnetic phases: Laves phases (cubic MgCu 2 (C15), hexagonal MgZn 2 (C14), and MgNi 2 (C36) polymorphs exist) are an important crystallographic structure class and form readily between RM and transition metals (TM) like Fe or Co. This makes RM interesting for the research of magnetic materials since Laves phases are crystallographic prototypes for various known hard magnetic crystal structures (CaCu 5 , Th 2 Ni 17 , Th 2 Zn 17 , ThMn 12 ) . In this respect, the magnetic potential of RMTM 2 and RMTM 5 phases are current subject of interest for screening and materials modelling for RE free hard magnetic phases (e.g., HfFe 5 ) .…”

“…This makes RM interesting for the research of magnetic materials since Laves phases are crystallographic prototypes for various known hard magnetic crystal structures (CaCu 5 , Th 2 Ni 17 , Th 2 Zn 17 , ThMn 12 ) . In this respect, the magnetic potential of RMTM 2 and RMTM 5 phases are current subject of interest for screening and materials modelling for RE free hard magnetic phases (e.g., HfFe 5 ) . Another promising material class for future permanent mag­nets are ferromagnetic phases crystallizing in tetragonal ThMn 12 structure.…”

Novel Permanent Magnets by High-Throughput Experiments

“…The methods applied are the highly accurate but slow density functional theory (DFT) or the less accurate but faster tight-binding-linear muffin-tin-orbitalatomic-sphere-approximation methods. HTS is deployed in searching for novel RE-containing and RE-free hard magnetic compounds 15,16 as well as, e.g., Heusler compounds. [17][18][19][20][21] On the experimental side, the most prominent high-throughput methods are the film libraries 22,23 and bulk 5,24 approaches to scan higher component systems for novel compounds within a reasonable time frame.…”